diff --git a/kiss b/kiss
index ff96c84..e5488e0 100755
--- a/kiss
+++ b/kiss
@@ -398,14 +398,15 @@ pkg_source_tar_hack() {
     tar xf "$_tmp_file_pre" ||
         die "$repo_name" "Failed to extract $1"
 
-    tar tf "$_tmp_file_pre" > "$_tmp_file" ||
+    # The sort command filters out all duplicate top-level
+    # directories from the tarball's manifest. This is an optimization
+    # as we avoid looping (4000 times for Python(!)).
+    tar tf "$_tmp_file_pre" | sort -ut / -k1,1 > "$_tmp_file" ||
         die "$repo_name" "Failed to extract manifest"
 
     # Iterate over all directories in the first level of the
     # tarball's manifest. Each directory is moved up a level.
-    while IFS=/ read -r dir _; do contains "$_seen" "${dir#.}" || {
-        _seen="$_seen $dir"
-
+    while IFS=/ read -r dir _; do case ${dir#.} in *?*)
         # Move the parent directory to prevent naming conflicts
         # with the to-be-moved children.
         mv -f "$dir" "$KISS_PID-$dir"
@@ -426,7 +427,7 @@ pkg_source_tar_hack() {
         # transferred out of it. This can't be a simple 'rmdir'
         # as we may leave files in here if any were copied.
         rm -rf "$KISS_PID-$dir"
-    } done < "$_tmp_file"
+    esac done < "$_tmp_file"
 
     # Remove the tarball now that we are done with it.
     rm -f "$_tmp_file_pre"